How Scientists Measure Lactate Thresholds in Runners Varies Widely, Review Finds

A systematic review of 70 studies has found that the methods used to identify the first and second lactate thresholds (LT1 and LT2) in running differ so widely across research that findings from different studies are often difficult to compare and interpret. The review, published in BMC Sports Science, Medicine and Rehabilitation, systematically classified assessment approaches into measurement-, calculation-, and prediction-based methods, and synthesized evidence on their validity, reliability, agreement, measurement error, predictive performance, and associations with running performance.

Blood lactate reflects the balance between lactate production and clearance during exercise, and lactate thresholds are widely used in endurance testing and training. Yet the review’s authors, led by Changda Lu, report that threshold definitions, reference standards, exercise protocols, and analytical procedures varied extensively across the included studies. The direct-versus-indirect distinction between methods was based simply on whether blood sampling was required.

The review followed PRISMA 2020 reporting guidelines and was retrospectively registered in PROSPERO (CRD420251276443) after the initial searches had been completed and screening had begun, but before screening was completed and data extraction began. The authors searched six databases across five platforms for records published from January 1960 to January 2026, with revised searches completed on 22 January 2026. From 1,706 records identified, 70 studies met the inclusion criteria.

Of the 70 included studies, 29 used prediction methods, 18 used calculation methods, 8 used measurement methods, 12 combined measurement and calculation approaches, and 3 combined calculation and prediction approaches. Prediction-based methods were the most common single category, reflecting a substantial body of work attempting to estimate thresholds without direct blood sampling at every stage.

The criteria used to define the thresholds themselves also diverged considerably. LT1 was identified using first rise, breakpoint, fixed concentration, and baseline-related criteria. The second lactate threshold was evaluated against a broader set of references, including maximal lactate steady state, the individual anaerobic threshold, fixed anchors, and other individualized methods. Because these criteria are not equivalent, the review concluded that the evidence did not support using maximal lactate steady state, individual anaerobic threshold, and onset of blood lactate accumulation interchangeably as LT2 criteria.

Among the LT2 criteria examined, maximal lactate steady state appeared to provide the most physiologically grounded reference, although the authors noted that confidence in this conclusion was moderate because definitions and protocols varied across studies. They advised that LT values should always be interpreted in relation to the reported definition and reference criterion, and that repeated assessments should use the same protocol.

The review also raised concerns about the quality of prediction-based research. For all 18 studies with an assessable model-development component, model development was rated as being of high concern for risk of bias. Overall evaluation risk of bias was rated high in 15 of 23 prediction-model or device studies, equivalent to 65.2 percent. This suggests that many prediction models and devices for estimating lactate thresholds may warrant cautious interpretation.

The authors note that the article is being shared early to provide faster access to peer-reviewed, accepted research; it is citable and carries a permanent DOI, but this version is subject to further edits and will be replaced by the final Version of Record. For coaches, athletes, and researchers using lactate thresholds to guide endurance training, the review’s central message is that a threshold value is only meaningful in the context of how it was defined and measured, and that comparisons across studies or repeated testing sessions require matching definitions and protocols.

Subject of Research: Methodological variation in the assessment of first and second lactate thresholds in running

Article Title: Methodological evolution in the assessment of first and second lactate thresholds in running: a systematic review

Article References: Lu, C., Zhu, Z., Wu, Y., Xing, Q., Wang, S., Du, S., Pan, B., & Shen, Y. (2026). Methodological evolution in the assessment of first and second lactate thresholds in running: a systematic review. BMC Sports Science, Medicine and Rehabilitation. https://doi.org/10.1186/s13102-026-02189-4

Image Credits: AI Generated

DOI: 10.1186/s13102-026-02189-4

Keywords: lactate threshold, LT1, LT2, running, systematic review, maximal lactate steady state, anaerobic threshold, exercise testing, risk of bias, endurance training, blood lactate, PRISMA